Moves all test runtimes to use derive_impl (#2409)

Step in https://github.com/paritytech/polkadot-sdk/issues/171

This PR adds `derive_impl` on all `frame_system` config impls for mock
runtimes. The overridden configs are maintained as of now to ensure
minimal changes.

---------

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

polkadot/xcm/xcm-builder/tests/mock/mod.rs

@@ -15,7 +15,7 @@
 // along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
 
 use frame_support::{
-	construct_runtime, parameter_types,
+	construct_runtime, derive_impl, parameter_types,
 	traits::{ConstU32, Everything, Nothing},
 	weights::Weight,
 };
@@ -76,6 +76,7 @@ parameter_types! {
 	pub const BlockHashCount: u64 = 250;
 }
 
+#[derive_impl(frame_system::config_preludes::TestDefaultConfig as frame_system::DefaultConfig)]
 impl frame_system::Config for Runtime {
 	type RuntimeOrigin = RuntimeOrigin;
 	type RuntimeCall = RuntimeCall;